Check if specific input file is empty

In my form I have 3 input fields for file upload:

<input type=file name="cover_image">
<input type=file name="image1">
<input type=file name="image2">

How can I check if cover_image is empty – no file is put for upload?

Answer

You can check by using the size field on the $_FILES array like so:

if ($_FILES['cover_image']['size'] == 0 && $_FILES['cover_image']['error'] == 0)
{
    // cover_image is empty (and not an error)
}

(I also check error here because it may be 0 if something went wrong. I wouldn’t use name for this check since that can be overridden)